Method for closing the ends of metal tubes



June 3, 1947. Q LANGQS 2,421,629

METHOD FOR. CLOSING THE END OF A METAL TUBE Filed Feb. 10, 1943 4 Sheets-Sheet 1 N 9 LL INVENTORQ OTTO A. LANGOS %,MW;

ATTORNEY June 3, 1947. Q A. L ANGOS 2,421,629

METHOD FOR CLOSING THEEND OF A METAL TUBE Filed Feb. 10, 1943 4 Sheets-Sheet 2 O O o O 9 O O O O O G O E O E O FIG.IB

m1 M u HLHIEHI m H! u u 1: n

INVENTOR. one A. LANGOS,

ATTORNE June 3, 1947. o. A. LANGOS 2,421,629

METHOD FOR CLOSING THE END OF A METAL TUBE Filed Feb. 10, 1943 4 sheets-sheet 3 WWW June 3, 1947. O; LANGQS "2,421,629

umnon FOR cnosme THE END OF A METAL-TUBE Filed Feb. 10, 1943 gets-Sheet 4 FIG. I2

FIG. is

FIG. II

I FIG. I5

FIG. IO

FIG. 14

I VENTOR BY 0T umeos ATTORNEY.

FIG. I3

Patented June 3, 1947 2,421,629 a, it

ivm'rnonl Fort CLOSING na nuns or ETA ES Otto A; Langos, Chicago, 1111. Application Eeb i ary 10, .1943, lfo.i l7 5,36l3 I v a 3 Claims." (CL ea -148.2) t t I The present invention relates to an improved method of defdrmingthe end portion of a tube.

and more particularly to an improved method of closing the end of a metal tube. The invention also relates to the improved pressure tight tube end closure structure which is obtained byutilizing the present improved method. Although gen erally applicable to the formation of end closures on both soft and hard metal tubes, of all sizes, dimensions and cross-sectional configurations, the improved method disclosed herein is particu larly applicableto the formation of pressure tight end closures on annealed steel or other workable ferrous metal tube blanks having around or oval cross-sectional configuration; I a

In general, the prior art practice of closing the ends of metal tubes is limited to the usecf spinningand swedging methods. The spinning method, wherein the work is turned at high speed while ahard metal tool, usually formed of tool steel, is brought to bear with increasing pressure against the metal of the tube end being worked upon, is limited to the working of soft metal tubes, such, for example, as those made of copper, brass, aluminum and other, soft non-ferrous metals. It has been found, in attempts to utilize production of tube end closures in large volumes, 2 regardless ofwhether the jtubes are formed of hard metal or soft metal. Moreover, in utilizing this method to work hard ferrous metalspsuch, for example, asannealed carbon steel, it is neces sary to preheat the metalto a workable state be: fore the fswedging operation can "be started and to maintain the metal in a workable sta'tefby reheating as the swedg ing operation progresses. Such heating causesa scaleto form onthe outer surface of the metal whichusually must belremoved by dippingthe metal in a pickling bath this method to formend closures on hard metal tubes, that an affinity between the tubefmetal and the tool is developed early in the process and long before an end closure. can be formed on the tube. Thisafiinity is probably caused by the heat resulting from the frictional engagement betweenthetube metal and the tool, and has the effect of causing the tube metal or the tool metal, or both, to bind and tearwhen the tool is, brought to bear under pressure against the spinning tube end. So ,far as is known, no tool material, steel or otherwise, is available which lacks afiinity for, workable ferrous metals and yet is hard enough to carryout the shaping of the tubemetal required during the. spinning operation.

Thus it is commercially impractical to employ conventional spinning ,methodsln the formation of end closures on hard metal tubes. More,-

over, this method as commercially employed in the formation of, end closures on soft, metal 'tubes is somewhat slow and must be practiced with care, sinceif the pressure oi the shaping tool against the endsidewallmetal of the'tube 'is be otherwise deformed at some weak point along itslength The method of swedging the end side wall metal of a tube to form anjend closure thereon is so slow and costly as to have little utility in the after the swedging is completedJ 'A further dis advantage of the swedging method resides inthe fact that regardless of the hardness of the metal worked upon, a smooth finished surface cannot be obtained. Accordingly, a finishing operation,

such, for example, as 1 grinding and polishing? is, in the manufacture of many articles, required after the "metal shaping been effected by swedging, This is also true offthe spinning method, although perhaps toa lesserdeg'ree.

7 I n general,itisjanobjectof thepresentfin vention to providean improved methodof clos mg theend of a metaltubefwhich is entirely free -W v dl mitati s-and mamas iages a ter n the n wn, inethodsfof 5pm; d swedging. l

More positivelystated, it isfan objett ofthe inventionto provide an improved method of,

forming end closures on tubes, method may be easily and cheaply practicedto produce he le q we u t eni a t s t a minimum of labor and with a minimum of readily obtainable and relatively cheap equipment. a It is anotherobject of the: invention toprovide an improved method of a the character described,

which is not limitedtoj the formation'ofend closures on'jtubes formed of so ft workablamaterials but may be ,employed with equal facility and at little or no additional cost in the forms.- tion of end closures onfhardmetaljtubes formed of workable ferrous metals and thellike. ab I A d 0 ane e bbict h lv ll lb the present improved methodmay be utilized to form an end closure which is, entirely finished,

whereby the machining operationsiusually; re-

quired in the production of an article o f this charc rerle n r ede In accordance with stlllanotherl obiefcto fthe invention, the present impr veq method may be employed to form a tube Jend closure which is pressure tight, contains noffls'sures extendingen.- tirely between the inside andthe outside surfaces continuous steps.

3 of the tube, and possesses great structural strength.

It is a further object of the invention to provide for sealing an end of a pressure chamber, an improved pressure tight end closure which is capable of withstanding high pressures, is of simple and economical construction, and may easily be manufactured in production quantities.

According to another and more specific object of the invention, the end closure is, during the formation thereof, provided with a portion having a small fissure therein which is exposed to any pressure developed within the chamber, and provisions are made in the structure for utilizing the pressure developed within the chamber to assist in preventing the fissure from expanding.

In brief, the objects as set forth above are real ized in accordance with-the present invention by utilizing a die molding method to shape the end. side wall metal of a tube progressively and in non- More specifically, the method comprises the steps of intermittently applying pressure to the end side wall metal of the tube both along the length thereof and radially inward, thereby to crowd the end side wall metal of the tube inward to form a mass disposedsubstantially in the center of the tube end, and then exerting pressure on the mass along a line substantially parallel to the longitudinal axis of the tube in order to close any fissure remaining in the mass. As each metal crowding operation proceeds, the thickness of the crowded mass of metal increases and the hardness of the metal increases. Accordingly, the pressure exerted during each intermediate crowding operation to produce a given amount of crowding must be substantially greater than that exerted on the metal during the preceding crowding operation. In order to prevent the increasing pressure applications from deforming the tube along its length, the end side wall metal of the tube is, during the first application of pressure thereto, extruded to provide a surface on the inner side thereof which bears against the end of an anvil disposed within the tube, and. this bearing'surface is progressively increased during succeeding pressure applications, thereby to transfer an increasing proportion of the pressure load from the barrel of the tube to the anvil. v

The invention, both as to the methodand the article produced thereby, together with further objects and advantages thereof, will best be understood by reference to the specification taken in connection with the accompanying drawings in which:

Figs, 1 and 2 are front and side views, respectively, of a die press which may be utilized in practicing the present invention;

Figs. 1A and 1B schematically illustrate a portion of the carriage rotating mechanism forming a part of the press shown in Figs. 1 and 2.

Fig. 3 is an underside view of the die carrying press head forming a part of the press shown in Fig.1, which illustrates the manner in which the metal shaping dies are disposed on'the under side of the head;

Fig. 4 is an end view of the die carrying press head shown in Fig. 3;

Fig. 5 is a detail view partially in section, illustrating the knockout device used for ejecting the tubes from the molding dies at the end of each pressure application;

Figs. 6' and 7 are top and side views, respectiveiy, of the stationary platform and rotatable ported by the anvils 24 during operation of the inclusive, of the drawings, the press there illusl trated is well adapted for use in practicing the present improved method in the manner explained below. In brief, this press comprises the usual pedestal H) which carries side frame members H and I2 joined at the top by across-v over piece [3. The L-shaped frame members H and I2 support the usual work platform M on the bases thereof, this platform in turn having a tube carriage l5 mounted for rotation onthe upper side thereof in a suitable manner. Ariccehtrio shaft I6, journaled in the frame members I l andl2 at the upper ends thereof, and carrying a driving pulley l! at one end thereof, isprovided for actuating a press head l8 which is arranged to coact with the tube carriage l5. More specifically, the head I8 is mounted upon the lower. end

of a ram l9 which is journaled on'the off-centerportion of the shaft in such a manner that the head l8 may be reciprocated alongavertical path without tilting during the up and .down'rnovement thereof. Guide rods 20 and Ti, laterally spaced apart and rigidly mounted upon-the sta-.

tionary platform M are provided, which extend through snugly fitting holes 22 and 23 provided in the head [8 and function to guide this head in its up and down movement.

The tube carriage l5 comprises a ro'und anvil plate l5a which is rigidly secured by means of' bolts I50 to a ratchet plate l5b' ha'vinfg' aportion of reduced diameter journaled 'in;a, matching re-' cess machined in the top side .of the platform I4. The plate l5a rigidly supports aplurality of tube anvils in the form of vertically extending steel posts 24 which are equally spaced apart and form a circle having a center coincident with the center of the plate. As best shown in Figs. 9 ,to 18, inclusive, of the drawings, each of the anvils 24 is provided with an upper end which forms a half globe, having the diameter of the anvil. At the upper central portion of each-rounded anvil end, a conical recess is provided which, in the illustrated arrangement, has surfaces diverging thirty degrees from the longitudinal axis of the anvil. 4

A plurality of shaping dies 25 are carried by the head I8 in a manner such that thev'may be brought to bear against the ends of 'tubes suppress. More specifically, the head. 18 comprises two plates um and l8b which, are provided with suitable die receiving recesses'a'nd are suitablyclamped together to retain the dies therebetween. As best shown in Fig. 3 of the drawings, the die receiving recesses are cut in the lower plate l8b. These recesses are arranged in an are which is coincident with the are formed by the anvils 24. More specifically, the recessesaresoarranged that with dies held therein, means orthe molding cavity in each die is coincident with the long axis of one of the anvils. fh-,the,illustrated arrangement and as shown'in Fi recesses are provided for receiving thirteen different shaping dies thus permitting a maximuiniof thirteen different shaping operations. Itv is understood, of

a part of the press shown specific number but it is illustrative. When, however,the present improved method is practiced in the specific manner described below, only nine different shaping dies are required. Of these nine dies, those which perform the first seven metal crowding operations are each provided with a hole extending through the die and into which the metal is crowded. For the purpose of preventing the tubes from sticking in these seven diesat the end of each shaping operation, the knockout arrangement illustrated in Fig. 5 of the drawings may be provided in conjunction with each die receiving recess of the head 18. This arrangement comprises aknockout'piece 26, disposed in a recess provided in the plate l8a opposite the die receiving recess in thepiate i817 and biased by a heavy spring 21 to engage a die 25 disposed in the die receiving recess. Each knockout element 26 is provided with a projection 26a of the appropriate size to enter the metal receiving hole provided in a die of given size.

These projections of course vary in. dimensions in accordance with the sizes of the particular die holes with which they are required to mate.

For the purpose of rotating the tube carriage i5 step by step, thereby to advance each tube supported by an anvil 24 so that it will be opervend to an eccentric pin' iil lanid is pin connected at its lower end to thelarzn' Sta of a rocker shaft 3|. This shaft is journaled in the legs of a U- shaped frame 32 mounted upon the platform l4, and carries a rocker arm 34 which is arranged to reciprocate an edge biased slide 35 engaging the teeth 36 of the ratchet plate l5b. The teeth of the ratchet plate l5b are angularly spaced apart by the'same number of radians as the anvils 24 carried by theplate I5a. In order to prevent the carriage l5 from'being retracted during theback stroke of the slide 35, a stop pawl 39 pivotally mounted upon the platform i4 and biased by the leaf spring 40 is provided to engage the teeth 35 of the ratchet plate 15 In adapting the illustrated press for use in forming end closures on metal tubes of i a given length and diameter, an anvil plate l5a carrying anvils 24 havinga diameter only slightly less than the internal diameter of the tubes, is employed. The anvils are of exactly the same'shape and length. More specifically, the anvil length is enough less than the length of each tube blank that a sufiicient amount of side wall metal remainsabove theend of the anvil to permit the end closure to be formed; This difference in the lengths of the anvils and the tubeblanks will, of

course, vary somewhat depending upon the wall thickness of the particular tube blank which is to have an. end closure formed thereon. A plurality Fig. 6 of the drawings, and thenine dies 25a to 251, inclusive, shown in Figs. 91; to 17, inclusive.

' of the 'drawinzaare to be used, these dies may be mounted in the head 18 in the manner ancl order indicatedin Fig. 3 of the drawings. A; .L.

After the press has been thus adapted for use, u

operation ofthe. press may be started, it being reducing mechanism from a lineshaft or an eleca.

tric motor. During each revolution of the shaft 3 [6, the head i8 is moved downward so that the dies 25 are positioned adjacent the rounded ends.

of the anvils 24, and isthen retractedto its raised position wherein sufllcient space is provided be-r tween thehead l8 and the ends of the anvils to permit tube blanks to be placed upon and removed from the anvils. Also duringeach revolution of the shaft N5, the slide is movedfrom its retracted position to its extended position and'then back to its retracted position to advancethetube carriage l5 one stepH'More specifically, the ro;- tarymovement of the shaft "5 isso related to the movement of the rocker arm 34 that the slide 35 is retracted during retraction of the head I 8 toits raised position, and only reaches its extended position to engage one of the' teeth 35 of the ratchet plate .I5b slightly after the head l8 reaches the. limit of' its downward movement.

, tained at the end of each increment "stood that after operation ofthe press -is under way, the operator can, during each interval when wall metal of the tube toward the center of the Thus the tube carriage I5 is only rotated from i a given position to the next succeeding position during upward movement of the head 18 when l thedies 25 are moving away from the anvils 24. By suitably adjustingthe position of the anvil plate [5a relative to the ratchet plate l5b to position nine of the anvils. directly beneaththe nine dies 25a to 25:; inclusive, the desired align mentbetween the anvils and the dies may be reof movement of the carriage i5. i

From the foregoing explanation it will be understood that. after operation of the press is initiated, the tube blanks may befed to the press oneor more at atime during each: interval whengthe head" l8 occupies its raised position. Thepress maybe fed by manually telescoping the tube 3 blanks over the vertically extending anvils 2L After each tube blank has been operated uponby each of the ninedies-25a to 25i,inclusive, it may be manually removed from its supporting anvil by the press operator. Thus it will be underthe'die carrying head l8 occupies its raised position, remove a finished tube from its supporting anvil and telescope a newtube blank over the-adjacent anvil from which a finished tube blank has just been, removed. Thus themanual operations required continuously to practice the present improved method are reduced to an absolute minimum. l i Referring now more particularly to the manner in which the end of a tube blank may beclosed by employing thepresentimproved method, it may be assumed that the blank '42, asshowniin Figs. 8 to 18, inclusive,of the drawings, is telescoped over the anvil 240, shown in Fig. 6 of;,the drawings. Thereafter and when the tube 42, as carried by the anvil fla, is rotatedwith the'cafriage 15 into a position beneath the first die 25a, it is subjected to the first metal shaping opera tion. More specifically, with the tube 42 in this surfacesoi! the die 25a are brought into engagement with the upper end of the tube during the downward movement of the head 18. Thus immediately the lower shaping surface of the die of the tube As the die 25a is brought. to its lowermost position, the inwardly tapering shaping surfaces thereof squeeze a segment of the end side wall metal of the tube into engagement with a segment of the rounded end of the anvil 24a, so that bearing surfaces are provided between the endof the anvil and the metal of the tube. In this regard it is noted that thetaper between the outer circumference of the entrant opening into the molding cavity of the die 25a and the metal receiving opening at the top of the die, is so proportioned that the pressure applied to the tube 42 along its longitudinal axis isinsuificient to cause the tube to buckleor be otherwise deformed at any weak point along its length. After the metal has been deformed through the action of the die 25a and duringthe initial retraction of the head l8, the tube knockout arrangement, as illustrated in Fig. of the drawings, functions to eject the tube 42 from the die 2541, thereby to maintain the tube positionedon the anvil 24a. Also during the retraction of the head l8, the carriage is rotated .to bring the anvil 24a and the tube 42 into a position beneath the die 25b. Thereafter, and during the second downward movement of the head 18, the shaping surfaces of the die 25?), upon engagement with the extruded end metal of the tube, further crowd this metal towards the center of the tube end and further increase the surface of this metal which bears upon the rounded end of the anvil 24a. From this point on, the progressive crowding of the end side wall metal toward the center of the tube endprogressively increases when the anvil 24a and the tube 42 are successively positioned beneath the dies 250 to 25g, inclusive, all in a manner which will be clearly apparent from a consideration of Figs. 11 to 15, inclusive, of the drawings. From an inspection of these figures, it will be observed that at each stage of the metal crowding procedure a pressure tight seal, by crowding the excess of metal which remains at the end of thetube following the seventh shaping operation, into the inverted conical shaped recess provided in the,

molding cavity of the die 25h.

*Froma consideration of Fig. 17 of the draw-.

ings, it will be observed that the shaping surfaces of the ninth die 251 follow the contour of a half globe. Accordingly, when the tube 42, as deformed in the manner shown in Fig. 16 of the.

drawings, is operated upon by the die 25:, the mass of excess metal forming the inverted cone at the center of the tube end is crowded into the conical recess provided in the central portion of the rounded end of the anvil 24a. During this particular operation, the end side wall metal of the tube which is utilized in forming the closure, is finished to present a smooth.. rounded,

outer surface, and the fissure extending therethrough is confined in its extent substantially entirely to the metal which is forced into the conical recess provided at the central end portion of the anvil 24a. Thus a pressure tight end closure is formed on the tube 42.

,To examine the above-described methodsomewhat more closely, it will be noted that at the end of each shaping operation an increasing proportion of the end side wall metal of the tube 42 is brought to bear upon the rounded end surface of the anvil 24a. This, of course, meansthat during the next shaping operation when pressure is applied to the tube along the longitudinal axis thereof, a greater proportion of the pressure load is removed from the barrelof the tube and transthe bearing surfaces between the end side wall I metal of the tube and the rounded end of the anvil 24a are increased, and also that the thickness of the mass of metal disposed at the end of the tube is progressively increased. This is accomplished by progressively decreasing the diameter of the openings at the tops of the dies into which the metal is forced at the different shaping stages.

From a consideration of Fig. 16 of the drawings, it will be observed that the die 25h, which is utilized to perform the eighth metal crowding operation, isnot provided with a metal receiving opening through the thickness thereof, but on the contrary is provided with an inverted conical recess exactly in the center of its molding cavity. Accordingly, at the end of the eighth shaping operation a small. mass of metal, formingsubstantially an inverted cone shaped tit, remains at the top center portion of the tube 42. At the end of the seventh shaping operation a small hair line fissure remains in the metal which is forced into the metal receiving opening of the die 259. This fissure is, during the eighth shaping operation, completely closed to provide order to effect a given amount of metal crowding.

This is true not only for the reason that, as the shaping of the metal proceeds, the thickness of the metal being worked upon is increased and the diameter of the excess metal being forced into themetal receiving openings of the dies is decreased, but for the additionalreason that the metal is progressively hardened during each shaping operation. i In other words, the' work hardness of the end side wall metal of the tube increases with each deformation thereof, utilizing the anvil 24a to carry an increasing proportion of the pressure load, however, the increasing pressure required to distort the metal during the later shaping stages, is prevented from buckling or otherwise deforming the tube at a point along its length. It will also be noted in this connection, that the initial step of ex: truding the end side wall metal of the tube 42 to provide a bearing surface between this metal and the rounded end of the anvil-24a, is of importance since it permits an increased pressure application at the second shaping stage without dangerof deforming the tube at a point along 7 its length.

From the foregoing explanationit rill be un- 77 derstood that the rate at which the end side wall metal of a tube may be deformed to form the desired end closure, depends upon a number of factors. Thus, the character of the metal In this regard it is primer tubes.

formed is offsoft metal, such, for example, as.

brass or copper, has a large diameter, and has thin walls, the deformation of the metal to formthe end closure may proceed at a rapid rate. On

the other hand, if thetube is formed of a hard workable ferrous metaL -such, for examplegas metalto form the end closure must necessarily proceed at a much slower rate. All of the above factors must be considered in the design of the molding cavities of the dies, and also, inthe'determination of the number-of shaping stages which must be used inobtaining the desired end closures. When, however, the method is to be utilized in the formation of end closures on tube blanks of uniform size, wall thickness and material, the number of shaping steps required and p the configuration of the molding cavities pro, vided in the dies may be readily determined on an experimental basis. In this regard it is noted that the limiting factor in determining the shapes of the molding cavities, and hence the number of shaping steps required, is the amount of pressure which may be applied along the long axis of a particular tube without causing the undesired deformation of the tube along its length.

It has been found that the above-described method of forming end closures on the ends of metal tubes on a production basis is of particular utility in closing the ends of theprimer tubes conventionally used in the. manufacture of shells, bombs, and the like. Prior to the advent of the present invention, the spinning method was em ployedin the formation of end closures on brass However such method was limited to materials such as brass which are soft enough to permit spinning. This excluded the use of steel tubing, and thus represented a serious handicap to. large volume, production from all suitable and available metals. The formation of the .tube blanks from steel tubing presented no problem to theprimer tube manufacturers, but the method of swedging was all that was available in the formation. of end closures on steel primer tubes and this method is expensive, and

generally unsatisfactory from a large volume,

high quality output standpoint. The presentimproved method represents a complete solution of this problem. closures on workable steel tubes of the character now available to the primer tube manufacturing industry may, by utilizing the present improved method, proceed at a rate equaling if not surpassing the rate at which end closures may be formed on brass primer tubes by utilizingthe spi'nning method referred to above.

It has been found that in forming end closures on annealed steel tube blanks having the following dimensions, the nine shaping steps illustrated in Figs. 9 to 17, inclusive, of the drawings and employing die molding cavities of substantially the configurations there shown, are sufiicient to provide a smooth rounded end closure which is wholly. free of fissures except possibly at the very inside surface and is absolutely pressure tight:

Tube length 3.25 Outside diameter of tube c .5625 Tube wall thickness 'In fact, the production of end Inches After a primer tube blank has been provided with i an end closure in the manner just explained, firing or explosion ports 42amay be formed in the H of the tube is, by extrusion, increased by approximately thesame amount. During each of the second to sixth shaping operations the diameter a of the extruded metal is decreased at the rate of .0625" for each step, while the overall length of the tube is not substantially altered. During the seventh shaping operation the diameter of the t extrudedmetal; is decreased by approximately .03125" and the overall length of the tube is also decreased slightly. During the eighth and ninth shaping operations the pressure is exerted pri I marily upon the mass of metalwhich haspbeen crowded to the center of the tube end. More spe-.

cifically, thigpressute isapplied along a lined which is substantially parallel to the longitudinal 1 axis of the tube, and is primarily applidt'nrough 1 this mass of metal tothe anvil24a. i

The finished end closure as formed upona steel primer tube in the manner just explained:

is illustrated in the sectionalized view shown in Fig. 18 of the drawings. From a consideration of this closure, itwill be notedthat after the closure is completed the excess metal which .projects within the pressure chamber of the tube forms a conical mass, theside surfaces ofwhich converge to a narrow end at the lowermost portion of themass and have abaseline along the body portion of the end closure. This small mass 1 of excess metal contains a small fissure which is a substantially coincident with the longaxis of the sidesof the fissure would tend toexpand. this fissureandmig'ht, if sufliciently great, cause a rupture of the end closure.

structure, however, the pressure developed within the tube chamber isalso exerted radiallyinward on the tapering side surfaces of theexcess metal 1 i a Since the area of these surfaces is greatly in excess of theexposed surface areaof the fissure, the pressure directed radially inward is farin. excessof that exerted portion of the closure.

against the side walls of the fissure and thus positivelyprevents the fissure from expanding. i This feature oflthe illustrated structure, is of 1 particular utility in the formation of primer tubes, since. any rupture of thetubemetal may i 1 cause segments of the metal tube expelled from the firing chamber of ,ashellintothe bore of the rifle wherein the shell is fired, to become lodged in the rifling and thus cause scoring of the rifling during a subsequent firing operation.

side walls thereof in the manner illustrated in Fig. 13 of the drawings, 'I'heseports are usually formed by a punching operation and define four equally spaced apart lines extending along the barrel of the tube. i

From the foregoing explanation it will be understood that the present invention is ofgreat utility in the metal tube art since it permits of the use of hard workable ferrousmetals in the 1 formation of tube blanks, while permitting closed ends to be formed on suchtubesfin production quantities and on a low unit cost basis. Moreover,the method is applicable to the formation of end closures on tubes madeofsofter metals at a per unit cost which is comparable, if not less than, that presently possible using the methods a .knownto the prior art, In this regardit is C With the illustrated 1 1 pointed out that the method is not limited to the formation of end closures on round tubes, but may be employed in closing the ends of tubes having oval, octagonal, square, or other CIOSS-SCCUOHEL. configurations. The shape of the closure which may be formed, utilizing the present improved method, is also not limited to that of a half globe, but may be different, depending upon the requirements of the particular tube application. It is noted further that the structure of the end closure formed by the present improved method is especially well adapted to the closing of tubes which are to be used as pressure chambers, since thepressure sealing action of the fissure remaining in the excess metal portion of the closure, positively precludes any rupture of the end closure due to the pressure developed within the tubechamber.

While one embodiment of the invention has been disclosed, it will be understood that various modifications may be made therein which are within the true spirit and scope of the invention.

I claim:

1. The method of closing the end of a cold hard metal tube about the end of an anvil disposed within the tube which comprises extruding the end side wall metal of the tube to provide a bearing surface between the extruded metal and the end of said anvil, and progressively crowding the extruded metal of the tube inward and against the end of said anvil by a series of pressure applications and in a manner such that the bearing surface of'the metal against the end of said anvil is increased upon each pressure application to offset the increase in pressure required to crowd the metal upon the next pressure application, whereby deformation of the tube along its length during the pressure applications is prevented.

2. The method of closing the end of a cold hard metal tube about the end of. an anvil disposed within the tube and provided with an excess metal cavity at its end, which comprises extruding the end sidewall metal of the tube to provide bearing surfaces between the extruded metal and the end of said anvil, progressively crowding the extruded metal inward by applying pressure to the tube at least partially along the length thereof, thereby to form a mass of metal disposed substantially in the center of the tube end, concurrently crowding the extruded metal against the end of said anvil to progressively increase the bearing surface of the metal against the end of said anvil in order .to close any fissure remaining'in said mass. 1

3. The method of closing the end of a cold hard metal tube about the end of an anvil which isdisposed within the tube and is provided with an excess metal cavity at its end, which comprises collapsing the end side wall metal of the tube radially inward to form a mass disposed substantially in the center of the tube end, and crowding said mass into said cavity in order to close any fissure remaining in said mass.

O'I'IO A. LANGOS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 529,597 Cayley et al Nov. 20, 1894 368,837 Kennedy Aug. 23, 1887 1,367,191 Leckie Feb. 1,1921 2,309,561 Westin et al Jan. 26, 1943 2,130,699 Reinartz- Sept. 20, 1938 389,087 Kennedy Sept. 4, 1888 1,538,610 Bast May 19, 1925- 2,069,858 Squires Feb. 9, 1937 537,014 Burton et al Apr. 9, 1895 1,309,773 Newell July 15, 1919 1,903,630 Minor Apr. 11, 1933 2,279,726 Allen Apr. 14, 1942 1,420,721 McNiff June 27, 1922 378,976 Ritchie Mar. 6, 1888 2,026,133 Mapes Dec. 31, .1935 1,471,952 Ford Oct. 23, 1923 331,528 Nason Dec. 1, 1885 339,812 Ritchie Apr. 13, 1886 612,496 Hathaway Oct. 18, 1898 800,056 Bailey Sept. 19, 1905 I FOREIGN PATENTS Number Country Date 18,320 Great Britain Aug. 9, 1909 172,914 Great Britain July 16, 1921 273,705 Italy Apr. 29, 1930 Great Britain Dec. 29. 1884 

